Process for making pitch-impregnated fiber pipe

ABSTRACT

Disclosed is a pitch-impregnated fiber pipe having a surface coating of pitch containing aluminum pigment. The method of manufacture comprises suspending unimpregnated, conventionally manufactured porous fiber pipe tubes in a suspension of aluminum powder in the liquid pitch and forcing the pitch into the pores and interstices of the fiber pipe tubes.

United States Patent [1 1 Gannon Dec. 23, 1975 PROCESS FOR MAKINGPlTCH-IMPREGNATED FIBER PIPE [75] Inventor: Charles R. Gannon, Ashland,Ky.

[73] Assignee: Ashland Oil, Inc., Ashland, Ky.

[22] Filed: Aug. 2, 1972 [21] Appl. No.: 277,290

Related US. Application Data [63] Continuation-impart of Ser. No.224,216, Feb. 7,

1972, abandoned.

[52] US. Cl 427/398; 106/281 R; 427/296;

427/442 [51] Int. Cl. B05D l/l8; F16L 9/14 [58] Field of Search 117/94,32, 158, 160 R,

[56] References Cited UNITED STATES PATENTS 1,465,107 8/1923 Wickel eta1 117/160 R X 1,587,750 6/1926 Bleecker 2,033,885 3/1936 Derby 117/158X 2,201,981 5/1940 Baron 117/160 R 2,223,289 11/1940 Lyons 106/281 R2,332,219 10/1943 Harshberger 117/32 X OTHER PUBLICATIONS Aluminum Paintand Powder, Edwards and Wray, pp. 64-65, Reinhold Publishing Corp.

Primary ExaminerWilliam D. Martin Assistant Examiner-Stuart D. Frenkel[57] ABSTRACT Disclosed is a pitch-impregnated fiber pipe having asurface coating of pitch containing aluminum pigment. The method ofmanufacture comprises suspending unimpregnated, conventionallymanufactured porous fiber pipe tubes in a suspension of aluminum powderin the liquid pitch and forcing the pitch into the pores and intersticesof the fiber pipe tubes.

5 Claims, No Drawings PROCESS FOR MAKING PITCH-IMPREGNATED FIBER PIPECROSS REFERENCES TO RELATED APPLICATIONS This application is acontinuation-in-part of co-pending US. application, Ser. No. 224,216,filed Feb. 7, 1972 now abandoned.

FIELD OF INVENTION This invention relates to: porous articles improvedfor certain purposes by being at least partially saturated withimpregnants; to a process for making such impregnated articles; and toimpregnant compositions. The invention is concerned in one specificembodiment with pitch-impregnated fiber pipe, a method for manufacturingthe same, and pitch-impregnant compositions.

PRIOR ART Porous articles are improved for certain purposes bysaturating them with an impregnant material, such as pitch. The desiredimproved properties obtained include increases in density, strength,durability, electrical resistance, insulating value, and resistance towater as well as decreased permeability and improved finish.

lmpregnants (impregnating materials), satisfactory for industrial use,have been formulated with pitches derived from water gas tar, oil gastar, petroleum tars and sludges, and wood tar. The primary sources ofpitch impregnants are coal tar pitch derived from the pyrolysis of coaland pitch derived from petroleum. These have been used by themselves, inblends, or in combination with resins, oils, waxes, and other modifyingadditives. Such impregnants are widely used in the manufacture ofroofings, water-proofing compounds, insulating papers and fabrics,building boards, electrical insulators and conduits, felts and belts,brake linings, ceramic bodies and bricks. Coal tar pitch and pitchderived from petroleum have found a particularly important use in themanufacture of bituminized fiber pipe for use in sewer and drainagelines and as conduit for power and telephone cables.

The manufacture of bituminous-impregnated fiber pipe is well known inthe prior art. Ordinarily a pulp slurry of a fibrous material first ismade. Newsprint is a common material for the pulp slurry, although othermaterials such as chemical pulp and asbestos fibers may also be added. Awet web of interfelted cellulose fiber is deposited from the slurry ontoa felt roll. Subsequently the web is wound onto a mandrel to form a tubeof a desired wall thickness. Each wet tube on a supporting mandrel isthen passed through a drying oven, and the mandrel subsequently isremoved. The result is a dry paper tube of a desired wall thickness.There are a number of methods of impregnating the dry paper tubes with awater-proofing impregnant, which ordinarily is molten pitch. Thesemethods include simple soaking of the paper tubes in the impregnant,pressure saturation, vacuum saturation or a combination of pressure andvacuum saturation.

In the combination method a number of the dry paper tubes are firstplaced in a pressure vessel and subjected to a vacuum for severalminutes. The vessel,

still at reduced pressure, isthenfilled with molten pitch until thepaper tubes are submerged. The molten pitch is circulated for a periodof time and the pressure in the 2 vessel is then restored to atmosphericpressure thereby causing the molten pitch to permeate the pore spacesand interstices of the paper tubes. The remaining molten pitch isdrained from the pressure vessel and the impregnated tubes are removedand quenched.

The pitch-impregnated tubes thus made are then ready for trimming of theends, machining and packaging for shipment. The pitch-impregnated fiberpipe thus manufactured is well suited for use as sewer pipe, undergroundconduit pipe for utility lines such as telephone cables and electricpower lines, and other uses where conditions of low pressures and highmoisture may be encountered. The pitch present in the pipe binds thecellulose fibers and imparts strength to the pipe as well as renderingit highly resistant to moisture. The fiber pipe is, however, notcompletely immune to the penetration of moisture. Under prolongedexposure to moisture, the pipe may eventually lose much of its originalstrength. A pitch-impregnated fiber pipe having increased moistureresistance thus is obviously desirable.

Pitch-impregnated fiber pipe is often stock-piled in open storage areaswhere it is exposed to temperature extremes, as well as to sunlight,rain, and snow. Consequently, over a period of time, the initiallyglossy black surface of the pipe deteriorates to a dull matte surface.Deterioration is thought to result primarily from exposure to theultraviolet fraction of sunlight. A fiber pipe possessing improvedresistance to exposure thus is highly desirable.

In the manufacture of fiber pipe coal tar has been as distinguished frompetroleum pitch, hasbeen preferred in the past. Coal tar pitch enablesthe manufacture of a fiber pipe having suitable moisture resistance andresistance to weathering. This is primarily caused by the carbonparticles (quinoline insolubles) in coal tar pitch which filter to theinside and outside surfaces of the pipe during the impregnation process,thus forming a protective coating which renders the pipe moistureresistant and enhances its weather-resistant characteristics. Petroleumpitch has been available more recently and has found use as animpregnant either in blends with coal tar pitch or by itself.

Fiber pipe produced with a petroleum pitch impregnant, which containsvery little suspended carbon particles, has, however, been found to beless resistant to moisture and to weathering than fiber pipe completelyimpregnated with coal tar pitch or blends of petroleum pitch and coaltar pitch. Petroleum pitch thus has not been completely accepted as asole impregnant for fiber pipe.

Although fiber pipe produced with coal tar pitch, or blends of coal tarpitch and petroleum pitch, exhibits excellent characteristics ofquality, persons exposed to the vapors during the impregnating processor to the coal tar pitch itself in the subsequent handling of the pipe,often experience skin irritation caused by the components of the coaltar pitch. In contrast, persons working with petroleum pitch by itselfhave not experienced this problem, thus making the use of petroleumpitch more desirable, particularly where ecological concern is of theutmost importance.

Another desirable property of pitch-impregnated fiber pipe would be asurface color other than the black color imparted by the pitch. Creatinga colored effect with sprayed coatings has been attempted in the past,but with little success. The solubility of pitch in the paint vehiclehas always created unattractive blotching duced friction requires lesseffort to pull bundles of cable through the pipe conduit.

An object of this invention; therefore, is to make a porous articlewhich is at least partially impregnated with an impregnant and has asurface film of impregnant containing at least partially dispersedaluminum pigment therein. Another object of this invention is to providea method of making such an article. Another object of this invention isto make a pitch-impregnated fiber pipe having improved resistance toattack by moisture and to weathering. Another object of this inventionis to enable the increased use of petroleum pitch either alone or incombination with other pitches as an impregnant for fiber pipe. Anotherobject of this invention is to provide a method of making apitchimpregnated fiber pipe having a uniform metallic surface. Stillanother object of this invention is to make available apitch-impregnated fiber pipe having uniform metallic interior surfaceswhich offer reduced friction resistance.

SUMMARY OF THE INVENTION In essence, this invention comprises: theprocess of impregnating porous articles with an impregnant containingsuspended aluminum particles; the article so impregnated having asurface-coating of impregnant containing suspended aluminum; and theimpregnant material itself. In one specific embodiment of the invention,bituminous impregnated fiber pipe is prepared by impregnating poroustubular forms with pitch containing suspended particulated aluminumtherein. In a still more specific embodiment, the fiber pipe isimpregnated with an unoxidized petroleum pitch containing a suspendedleafing aluminum pigment.

DETAILED DESCRIPTION OF THE INVENTION Generally speaking the article tobe impregnated, such as a building board, brick, ceramic body, roofingfelt, or fiber tube, must be sufficiently permeable to enablepenetration of the impregnant when the latter is applied to the surface.The article further must be stable at the temperature of impregnation.

The impregnant (the impregnating material) should have a low viscosityat the impregnating temperature to enable sufficient penetration intothe article being treated. The impregnant material must, however, bereasonably hard at ambient service temperatures. In addition, it isdesirable that the impregnant be low in filterable suspended matter(carbonaceous solids, dirt and mineral ash) particularly since aluminumparticles are to be added. If too much filterable suspended material isincluded, unsightly surface deposits on the finished article can resultor impregnation can be incomplete. The quantity of suspended matter thatcan be tolerated in the impregnant material will depend upon the articleto be treated (its nature, porosity, and wall thickness), the particlesize of the suspended material, viscosity of the impregnant fluid, andthe method of impregnation. Test methods of determining filterablespresent in impregnant materials are known in the prior art. Otherproperties desirable in the impregnating material, particularly if hightemperatures and vacuums are used, are limits on the content of lowboiling volatile materials, flash and fire point, and toxicity. A numberof bituminous materials meeting these requirements are availableincluding coal tar and petroleum pitches.

Any commercially available aluminum pigment can be used in thisinvention. The system of grading and classification of aluminum powdersand paste varies according to the individual manufacturer. One of themost commonly accepted classifications of aluminum pastes and powders isthat of The American Society for Testing Materials. This ASTMclassification is as follows:

Table I ASTM Designation 962 66 Maximum Amount Retained on a No. 325 (44u) Sieve The amount of aluminum pigment (powder or paste) added to theimpregnant is determined by a number of factors. Aluminum pigments areexpensive. Accordingly, the amount added should only be that necessaryto provide a proper coating on the article being treated. The minimumamount will be that necessary to achieve a desired improvement in theproperties of the acticle.

As to the manner of impregnating an article with impregnant containingsuspended aluminum, any of the methods presently used in the art can beemployed. These include simple soaking in an open tank over a period oftime, pressure saturation, vacuum saturation, and combined pressure andvacuum saturation. This last method is a preferred method and is morefully discussed in a following portion of the description.

As noted previously, a more specific embodiment of this invention is themanufacture of bituminous impregnated fiber pipe in which fibrous tubesare impregnated with a pitch impregnant containing suspended aluminumpigment therein. In this particular embodiment the fibrous tubes to beimpregnated are of the kind presently used in conventional fiber pipemanufacturing. As discussed previously, they are made by winding a wetweb of cellulose pulp on a mandrel to the desired wall thickness andthen drying the tube either before or after it had been removed from themandrel. The technique of forming these dried paper tubes is well knownin the art and is discussed briefly in US. Pat. Nos. 1,803,409;1,854,230; and 1,860,674.

The pitches commercially available for manufacturingbituminous fiberpipe include coal tar pitch and petroleum pitch. Petroleum pitch, atleast for the purposes of describing this invention, may be eitheroxidized petroleum pitch or unoxidized petroleum pitch. Oxidizedpetroleum pitch is familiar to those skilled in the art, and is derivedby air blowing certain petroleum refinery flow streams to obtain adesired pitch product.

Unoxidized petroleum pitch can be further characterized as unmodifiedthermal petroleum pitch. These pitches remain rigid at temperaturesclosely approaching their melting points. The preferred procedure forpreparing the unoxidized petroleum pitch uses as startcracking is notsufficiently severe to remove substan- 1 tially all paraffins from theslurry oil orcycle oil, they may be extracted with furfural. In eithercase, the resultant starting material is a highly aromatic oil boilingat about 700 to 850F. This oil is thermally cracked at elevatedtemperatures and pressures for a time sufficient to produce a thermallycracked petroleum pitch with a softening point of about 150 to about210F. The manufacture of unoxidized petroleum pitches is described inU.S. Pat. Nos. 2,768,119 and 3,140,248. Table 11 presents comparativeproperties of four unoxito the fact that certain metallic pigments occurin the form of thin flakes. When such pigments are mixed with a vehicleand applied as a paint film, the thin flakes float and concentrate atthe surface of the paint film where they overlap each other. Aluminumpowder is treated with a leafing agent such as stearic acid to render itleafing, as well as to reduce the hazard of explosion. Leafing aluminumpigment can be prepared by grinding aluminum in a ball mill in thepresence of mineral spirits or similar solvents. The mixture is thenfiltered to yield an aluminum paste. A typical leafing aluminum pigmentavailable commercially in paste form has the compositions shown in Table111.

TABLE III dized petroleum pitches (A, B, C and D) and an oxi- 15 dizeditch Non-volatile content 68.0% minimum p Screen retention 325 mesh14.0% maximum TABLE I1 Test Test Method Pitch A Pitch B Pitch C Pitch DPitch E Softening Point, F., R&B ASTM D-2398 173 174 168.5 166 174Density, G/CC Mettler 1.192 1.205 1.160 1.178 1.186 Mod. Con. CarbonWt.% ASTM D-2416 37.81 43.8 39.6 36.9 37.1 Flash ASTM D-92 540 495 545535 480 Pen. 100/5/77 ASTM D-5 0 0 0 0 0 Pen.200/60/1l5 ASTM D-5 128 47208 123 Pen. 50/60/15 ASTM D-5 40 37 68 48 Sulfur, Wt.% ASTM D-l552 2.731.47 2.01 0.95 1.69 Benzene lns., Wt.% ASTM D-23l7 0.80 11.7 1.9 2.3 8.1Qumolme lnsoL, Wt.% ASTM D-2318 0.11 (1) Nil Nil Nil Viscosity, CPS 350Brookfield 40 70 45 2 70 p 325 Brookfield 60 110 82.5 65 12s RPM) 300Brookfield 140 230 165 135 240 (1) Quantity of solids content too greatto permit filtering At the time of filing the parent application, Ser.No. 224,216, it was thought that a leafing aluminum in combination withan unoxidized petroluem pitch was necessary to obtain the desiredimprovement in resistance to water and in weathering. This limitationappears necessary only if it is desired to produce a fiber pipe producthaving smooth, metallic-colored or aluminized exterior and interiorsurfaces. Thus, any aluminum pigment, particularly any of thosedescribed in Table I, can be used in combination with coal tar pitch,unoxidized (thermal) petroleum pitch, oxidized petroleum pitch ormixtures of these.

The amount of aluminum powder or paste pigment added to the pitchimpregnant will, of course, vary. The minimum amount will be thatrequired to achieve a desired level of resistance in the finishedproduct to moisture or weathering. The maximum amount will be determinedby the economics of the process and the possibility of unevenpenetration of pitch if too much filterable aluminum pigment issuspended in the pitch lmpregnant. Ranges of 0.1 to 1.4 or preferably0.3 to 0.7 of aluminum pigment in a mixture of pitch and aluminum can beused. These values for the aluminum concentration are based on aluminumalone and do not include any additional solvents or stabilizingmateriais which may be present. The ranges given are not restrictive.Less or greater concentrations of aluminum can be added.

. lf pitch-impregnated pipe is to be manufactured havmg, in addition toimproved moisture and weathering resistance, metallic or aluminizedexterior and interior surfaces, the best results are obtained if aleafing-type aluminum pigment is used in combination with an unoxidized(thermal) petroleum pitch. The term leafing 18 well known to those inthe art and is defined in Federal Test Method Standard No. 141. Leafingrefers Moisture content 0.1% maximum Solvent present Mineral SpiritsBulking Value 0.080 al. per lb. Weight per Solid Gallon 12.45 bs.Particle Size Distribution 440.5 microns 44-150 microns 7% It has beendetermined that some non-leafing aluminum powders, when combined with anunoxidized petroleum pitch, will also yield a metallic-colored oraluminized pipe. It is believed that in these cases the stabilizingagent added to the aluminum pigment to render it non-leafing is in factdecomposed .when the aluminum pigment is heated to the temperature ofthe molten petroleum pitch, and that subsequently the aluminum pigmentacts as a leafing aluminum. Thus, although leafing aluminum powders arepreferred in the specific application of the invention to manufacturethe metallic-colored or aluminized pipe, non-leafing aluminum powders,which will function as leafing pigments at the temperature ofimpregnation, can also be used.

Returning now to the broader concept of making a pitch-impregnated fiberpipe using any of the commercial aluminum pigments available as well asany of the common pitches available, these two materials can be combinedin several ways to make the impregnating material. If the aluminumpigment has been supplied in paste form with a liquid carrier, the pastecan be manually added to the mass of molten pitch and the mixtureagitated by stirring or circulation. For impregnating purposes, thetemperature of the aluminum powderpitch mixture can be in the range of275 to 375F. This temperature will, of course, vary depending upon theproperties of the particular pitch.

The step of impregnating the dry paper tubes can be perfonned in anymanner which will force the pitch into the pores and interstices of thepaper tubes. A preferred method is one wherein the paper tubes areplaced in a pressure vessel and subjected to a vacuum for a number ofminutes. The molten aluminum powder-pitch mixture is then pumped intothe pressure vessel until the tubes are submerged. The molten mixture iscirculated for a period of minutes to insure an even distribution ofpitch and aluminum. The pressure final impregnant composition. Theoutside diameter of the pipe was 4 7/16 inches and the wall thicknesswas one-fourth inch. Samples of each specimen were then tested. In thecopending parent application, data from tests having less relevance wasincluded in the test results reported. Only the data from those testsdeemed most relevant are included in this specification and are asfollows:

99.32% Petroleum Coal Tar Pitch Pitch (U0) ASTM 2311 85% Petroleum Pitch(U0) 0.68% Aluminum Specification Creep (23 hr.)" .100 inches avg. .084inches Water absorption 1.04% average .75 & .60% 2% Max. Dry CrushingStrength, lb./ft. 800 average 920 800 Flattening .80% average .69 & .65%3% Max.

"lnches of creep per two-inch section of pipe under 1000 psi at 68F,after 23 hours.

"Percentage weight gain of original weight after 48 hours submersion inwater at 70F and atmospheric pressure. Load at rupture point in poundsper linear foot.

"Percent reduction in diameter under 80 lbs/linear foot at 120F.

in the vessel is then raised to atmospheric pressure thereby forcing thepitch into the pore spaces of the paper tubes. The remaining moltenpitch-aluminum powder mixture is then drained from the vessel, and thetubes are withdrawn and quenched.

It is not completely understood as to what phenomenon occurs. There is,of course, a filtering action in which the suspended aluminum powder isretained in a film of pitch on the surfaces of the paper tubes. Ifpitch, other than 100 unoxidized petroleum pitch, and

From the preceding table it will be noted that all properties of thealuminized pipe were improved over those of pipe prepared with aconventional impregnating pitch.

Additional samples of fiber pipe impregnated with petroleum pitch (pitchsample D, Table II) containing various concentrations of suspendedaluminum powder were prepared and tested. The pipe diameter again was 47/ 16 inches o.d. and the wall thickness one-fourth inch. Results wereas follows:

Pipe Dry lmpregnant Water Crushing Sample Composition Creep (1)Absorption (2) Strength (3) Flattening (4) A 0% Aluminum 100% PetroleumPitch (5) 0.72 avg. 1.61-1.94 800 1.81-3.87 B .17% Al. (6) 0.70 avg.1.48-1.83 840-800 1.96-2.10 C .34% Al. (6) 0.68 avg. 1.58-1.57 (7) 7202.04-2.18 D .68%AI. (6) 0.72 avg. 1.17-1.26 760-700 1.06-1.37 E 1.36%Al. (6) 0.51 avg. 0.63-0.60 920-1000 0.96-1.31

(1) Inches of creep per two-inch section of pipe under 1000 psi at 68F,after one hour.

(2) Percentage weight gain of original weight after 48 hours submersionin water at 70F and atmospheric pressure. (3) Load at rupture point inpounds per linear foot.

(4) Percent reduction in diameter under lbs/linear foot load at 120F.

(5) Unoxidized (thermal) petroleum pitch in all tests.

(6) Percent of aluminum in total mixture.

( 7) This anomaly is attributed to experimental error.

aluminum powder, other than leafing aluminum powder, are used, thepresence of aluminum powder in the film of impregnant on the surface ofthe pipe is less readily apparent and may be completely masked. Usuallyvisual examination of the pipe surface, however, shows a metallic glintin the black surface. If unoxidized petroleum pitch and leafing aluminumhave been used, the aluminum particles because of their leafing actiontend to stay on the film surface yielding a pipe with a metallicaluminized surface.

The improved properties of aluminum powder-pitch impregnated fiber pipemade by this improved process have been demonstrated. In one test, aspecimen of pipe was prepared using a standard commercial impregnantcomprising 15% coal tar pitch and unoxidized petroleum pitch. A secondspecimen was prepared using unoxidized petroleum pitch corresponding tosample D from Table II mixed with powdered aluminum having theproperties shown in Table III. The concentration of aluminum powder was0.68% in the Sections of pipe samples A, B and C were tested in aconventional weatherometer for 619 hours, (the equivalent of 18 monthsoutdoor exposure).

lmpregnant Observation 0% Aluminum Petroleum Pitch Surface was dull.dusty brown. .17% Aluminum Some evidence of aluminum-fiber surface stilldull. 34% Aluminum Bright aluminum coating and film.

No dusting evident.

1% Aluminum 99% Petroleum ASTM 20% Coal Tar Pitch 100% Petroleum Pitch(U) D1861 80% Petroleum Pitch (U0) Pitch (U0) Range Avg. Standard WetCreep .56 .38 .30.46 .375 Water Absorption 1.13% 1.26% .78-1 .02% 90% 2%Max. Water Absorption (200 hours) m 3.37% 3.85% 2.0-3.8% 2.82% DryCrushing Strength,lb.lft. 1140 1160 ll001262 1165 1250 Mm. Flattening1.10 1.47 .78l.62% 1.17% 3% Max.

U0 indicates unoxidized petroleum pitchv Dry sample immersed in waterand loaded at 1000 psi fiber stress for 336 hours (two weeks). mPercentage weight gain 01' original weight after 48 hours submersion inwater at 70F and atmospheric pressure. Percentage weight gain oforiginal weight after 200 hours submersion in water at 70F andatmospheric pressure.

Load at rupture point in pounds per linear foot. Percent reduction indiameter under 80 lbs/linear foot at 120F.

" During this plant test the dry paper tubes were of reduced quality.The reduced crushing strength is thought to have resulted from thereduced paper tube quality.

In another test a sample of pipe impregnated with an impregnantcomprising coal tar pitch, 1% aluminum and the remainder unoxidizedpetroleum pitch exhibited only 0.73 percent water absorption aftersubmersion in water for five days. The average amount of absorption of apipe sample impregnated only with 20% coal tar pitch and 80% petroleumpitch after five days would be about 1.5 percent.

Increased ease in handling aluminized pipe sections has been noted bypersons manually working with them. Aluminized pipe exposed to thesummer sun does not heat to as high a temperature as conventional blackpitch impregnated pipe. The aluminized pipe thus can be handled moreeasily with bare hands or thin gloves. Personnel have also noted thataluminized pipe sections are easier to load because the pipe lengthsmore readily slide over each other than do the conventional black pitchimpregnated pipe lengths. Unless specifically indicated otherwise hereinall percentage compositions listed herein are compositions by weight.

I claim:

1. A process for manufacturing a pitch-impregnated fiber pipe having ametallic-colored surface comprisa. forming a tabular body of interfeltedfibrous material;

b. immersing said tubular body of (a) in a liquid impregnant consistingessentially of molten unoxidized petroleum pitch and suspended leafingaluminum pigment of ASTM designation 962-66:

0. forcing said liquid impregnant of (b) into the pore spaces andinterstices of said tubular body: and

d. removing said tubular body from said liquid impregnant and quenchingsaid tubular body; thereby forming a pitch impregnated fiber pipe havinga metallic-colored surface.

2. The process of claim 1 wherein the concentration of aluminum pigmentin said liquid impregnant is at least about 0.1 percent by weight.

3. The process of claim 1 wherein the concentration of aluminum pigmentin said liquid impregnant is at least about 0.3 percent by weight I 4.The process of claim 1 wherein said tubular body of (a) comprisesinterfelted cellulose fibers.

5. A process for manufacturing a pitch-impregnated fiber pipe having ametallic-colored surface comprisa. forming a tubular body of interfeltedfibrous material;

b. immersing said tubular body of (a) in a liquid impregnant consistingessentially of molten unoxidized thermal petroleum pitch and suspendedaluminum pigment of ASTM designation 962-66, said pigment being anon-leafing pigment which functions as a leafing pigment at thetemperature of the molten pitch;

c. forcing said liquid impregnant of (b) into the pore spaces andinterstices of said tubular body and d. removing said tubular body fromsaid liquid impregnant and quenching said tubular body;

thereby forming a pitch impregnated fiber pipe having a metallic coloredsurface.

1. A PROCESS FOR MANUFACTURING A PITCH-IMPREGNATED FIBER PIPE HAVING AMETALLIC-COLORED SURFACE COMPRISING; A. FORMING A TUBULARBODY OFINTERFELTED FIBROUS MATERIAL; B. IMMERSING SAID TUBULAR BODY OF (A) IN ALIQUID IMPREGNANT CONSISTING ESSENTIALLY OFMOLTEN UNOXIDIZED PETROLEUMPITCH AND SUSPENDED LEAFING ALUMINUM PIGMENT OF ASTM DESIGNATION 962-66;C. FORCING SAID LIQUID IMPREGNANT OF (B) INTO THE PORES SPACES ANDINTERSTICS OF SAID TUBULAR BODY; AND D. REMOVING SAID TUBULAR BODY FROMSAID LIQUID IMPREGNANT AND QUENCHING SAID TUBULAR BODY;THEREBY FORMING APITCH IMPREGNATED FIBER PIPE HAVING A METALLIC-COLORED SURFACE.
 2. Theprocess of claim 1 wherein the concentration of aluminum pigment in saidliquid impregnant is at least about 0.1 percent by weight.
 3. Theprocess of claim 1 wherein the concentration of aluminum pigment in saidliquid impregnant is at least about 0.3 percent by weight
 4. The processof claim 1 wherein said tubular body of (a) comprises interfeltedcellulose fibers.
 5. A process for manufacturing a pitch-impregnatedfiber pipe having a metallic-colored surface comprising; a. forming atubular body of interfelted fibrous material; b. immersing said tubularbody of (a) in a liquid impregnant consisting essentially of moltenunoxidized thermal petroleum pitch and suspended aluminum pigment ofASTM designation 962-66, said pigment being a non-leafing pigment whichfunctions as a leafing pigment at the temperature of the molten pitch;c. forcing said liquid impregnant of (b) into the pore spaces andinterstices of said tubular body and d. removing said tubular body fromsaid liquid impregnant and quenching said tubular body; thereby forminga pitch impregnated fiber pipe having a metallic colored surface.